Various machines are known for the processing and separation of solid granular or solid particulate materials. Such sorting devices and graders often include one or more hollow cylinders, each of which can be rotated about its central axis by some form of drive means. The hollow cylinder includes a means for input of the granular or particulate material, and some other means to collect different portions of the material that have been sorted or graded according to their size, (e.g. length, width or thickness), or other physical characteristics. The input and output means, optionally together with other components, may permit either batch or continuous processing of the particulate material. Depending upon their intended use and the materials to be processed, the machines use different types of cylinders, each with carefully designed features that facilitate the sorting process. The configuration of the cylinder, combined with the forces generated by rotation of the cylinder, and other rotating components within the cylinder, determine the way in which the material is processed or sorted.
For example, some cylinders include an array of small perforations about the main curved surface of the cylinder, the perforations having sufficient size to permit narrower particles to pass through, but of insufficient size to permit wider particles to pass through. In this way, rotation of the cylinder about its central axis causes particles retained within the cylinder to be thrown about and against the internal walls of the cylinder. Narrower particles exit the cylinder through the perforations assisted by the centrifugal force of the rotating cylinder, whereas wider particles are retained within the cylinder for later collection. Often, perforated cylinders are used to separate granular products according to the width and/or thickness of the particles. Optionally, an agitator may be mounted co-axially within the cylinder to assist in the movement of the granular material about the inside of the cylinder.
Other examples of cylinder types include those with indentations (rather than perforations) about the internal surfaces of the cylinder, again to cause material within the cylinder to be separated into distinct portions. Often indented cylinders are employed within indent length grading machines (sometimes known as triers) to separate granular products according to the length of the particles. The indentations on the internal curved surface of the cylinder are sized such that particles having a length similar to or less than the length of the indentations are retained within the indentations and lifted as the cylinder rotates. Eventually, as the cylinder continues to rotate, the lifted particles fall from the indentations under gravity, to be caught by a trough typically mounted within a central region of the cylinder. A screw conveyor or auger may also be associated with the trough to assist in movement of the liftings portion of the material caught by the trough. In contrast, the tailings portion retained in the outer or lower regions of the cylinder may be removed by another outlet.
U.S. Pat. Nos. 3,612,273, 4,469,230, and 6,253,928, which are incorporated herein by reference, provide just three examples of prior patent documents that disclose such sorting machines and devices.
However, grading machines are often large and difficult to service. The grading cylinders may be difficult to replace due to their size and weight, or because of general access to the cylinder(s) in the grading machine. Typically, a grading cylinder must be lifted bodily out of a grading machine for service, or for insertion of a different type of cylinder into the grading machine. This is illustrated with reference to FIG. 1, derived from FIG. 6 of U.S. Pat. No. 4,469,230, which is incorporated herein by reference. Here it may be observed that a user of the machine wishing to replace sorting cylinder 11 must physically lift the cylinder from the machine via an opening or space alongside the cylinder. Not only does this require significant effort by the user, but clear access must be provided for cylinder removal and/or replacement. This may be difficult in an industrial setting, such as a busy factory floor. In other examples known in the art, access to the cylinder may be provided from above, such that the cylinder must be hoisted up and out of the machine.
At times due to the size of the grading cylinders or the configuration of the grading machine, the grading cylinders must be dismantled within a grading machine prior to their removal. For example, at times it may be desirable to retain a specific screw conveyor or agitator in position within a grading machine, and replace only the grading cylinder either with one of different properties, or for servicing of the machine. To this end, some grading machines require the use of “split cylinders” comprising two halves or several sections to be separated prior to cylinder removal. Such cylinders require re-assembly prior to their use in a grading machine, or re-assembly within the machine interior. Significant skill is required to ensure proper re-assembly of a split cylinder. Improper establishment of joints between the cylinder sections may result in poor rotation of the cylinder and damage to the cylinder or machine components.
Alternatively, other machines involve the use of whole cylinders that cannot be split or disassembled into separate sections. Typically, such cylinders must be removed from grading machines together with any components retained internal to the cylinders during operation (e.g. agitators, screw conveyors, troughs and the like).
Thus, whilst many machines and devices are known in the art for the sorting, grading or separation of solid granular or solid particulate materials, such machines and devices are often cumbersome and difficult to maintain and service. Often, the insertion and removal of cylinders, either for servicing or to change the configuration of the machine, can be very time consuming. There is a need in the art for versatile grading machines that permit quicker-changing of grading cylinders.